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Caching Driver
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<h1>Caching Driver</h1>

<p>CodeIgniter features wrappers around some of the most popular forms of fast and dynamic caching.  All but file-based caching require specific server requirements, and a Fatal Exception will be thrown if server requirements are not met.</p>

<h2>Table of Contents</h2>
<ul>
	<li><a href="#example_usage" title="Example Usage">Example Usage</a></li>
	<li><a href="#function_reference" title="Function Reference">Function Reference</a></li>
</ul>

<h3>Available Drivers</h3>
<ul>
	<li><a href="#apc" title="APC Cache">Alternative PHP Cache (APC) Caching</a></li>
	<li><a href="#file" title="File Caching">File-based Caching</a></li>
	<li><a href="#memcached" title="Memcached">Memcached Caching</a></li>
	<li><a href="#dummy" title="Dummy Caching">Dummy Cache</a></li>
</ul>

<h2 id="example_usage">Example Usage</h2>

<p>The following example will load the cache driver, specify <a href="#apc" title="APC">APC</a> as the driver to use, and fall back to file-based caching if APC is not available in the hosting environment.</p>

<code>
$this->load->driver('cache', array('adapter' => 'apc', 'backup' => 'file'));<br />
<br />
if ( ! $foo = $this->cache->get('foo'))<br />
{<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;echo 'Saving to the cache!&lt;br />';<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$foo = 'foobarbaz!';<br />
<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;// Save into the cache for 5 minutes<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$this->cache->save('foo', $foo, 300);<br />
}<br />
<br />
echo $foo;
</code>

<h1 id="function_reference">Function Reference</h1>

<h2>is_supported(<var>driver</var>['string'])</h2>

<p>This function is automatically called when accessing drivers via <samp>$this->cache->get()</samp>.  However, if the individual drivers are used, make sure to call this function to ensure the driver is supported in the hosting environment.</p>

<code>
if ($this->cache->apc->is_supported())<br />
{<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if ($data = $this->cache->apc->get('my_cache'))<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;// do things.<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<br />
}
</code>

<h2>get(<var>id</var>['string'])</h2>

<p>This function will attempt to fetch an item from the cache store.  If the item does not exist, the function will return <samp>FALSE</samp>.</p>
<code>$foo = $this->cache->get('my_cached_item');</code>

<h2>save(<var>id</var>['string'], <var>data</var>['mixed'], <var>ttl</var>['int'])</h2>

<p>This function will save an item to the cache store.  If saving fails, the function will return <samp>FALSE</samp>.</p>
<p>The optional third parameter (Time To Live) defaults to 60 seconds.</p>
<code>$this->cache->save('cache_item_id', 'data_to_cache');</code>

<h2>delete(<var>id</var>['string'])</h2>

<p>This function will delete a specific item from the cache store.  If item deletion fails, the function will return <samp>FALSE</samp>.</p>
<code>$this->cache->delete('cache_item_id');</code>

<h2>clean()</h2>

<p>This function will 'clean' the entire cache.  If the deletion of the cache files fails, the function will return <samp>FALSE</samp>.</p>

<code>$this->cache->clean();</code>

<h2>cache_info()</h2>

<p>This function will return information on the entire cache.</p>

<code>var_dump($this->cache->cache_info());</code>

<h2>get_metadata(<var>id</var>['string'])</h2>

<p>This function will return detailed information on a specific item in the cache.</p>

<code>var_dump($this->cache->get_metadata('my_cached_item'));</code>

<h1>Drivers</h1>

<h2 id="apc">Alternative PHP Cache (APC) Caching</h2>

<p>All of the functions listed above can be accessed without passing a specific adapter to the driver loader as follows:</p>
<code>$this->load->driver('cache');<br />
	$this->cache->apc->save('foo', 'bar', 10);</code>
<p>For more information on APC, please see <a href="http://php.net/apc">http://php.net/apc</a></p>

<h2 id="file">File-based Caching</h2>

<p>Unlike caching from the Output Class, the driver file-based caching allows for pieces of view files to be cached.  Use this with care, and make sure to benchmark your application, as a point can come where disk I/O will negate positive gains by caching.</p>

<p>All of the functions listed above can be accessed without passing a specific adapter to the driver loader as follows:</p>
<code>$this->load->driver('cache');<br />
	$this->cache->file->save('foo', 'bar', 10);</code>

<h2 id="memcached">Memcached Caching</h2>

<p>Multiple Memcached servers can be specified in the memcached.php configuration file, located in the <samp>application/config/</samp> directory.

<p>All of the functions listed above can be accessed without passing a specific adapter to the driver loader as follows:</p>
<code>$this->load->driver('cache');<br />
	$this->cache->memcached->save('foo', 'bar', 10);</code>

<p>For more information on Memcached, please see <a href="http://php.net/memcached">http://php.net/memcached</a></p>

<h2 id="dummy">Dummy Cache</h2>

<p>This is a caching backend that will always 'miss.'  It stores no data, but lets you keep your caching code in place in environments that don't support your chosen cache.</p>

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